what could tessie might have done at the end of the story that could have resulted in some change.

Probably not too much. The running theme of this story is the ingrained nature of this twisted tradition. Still there are sins that younger people are questioning the practice. We hear talk of other villages stopping the practice. Tessie might have appealed to them but the crowed expected this spectacle to unfold as it always does. Instead of making excuses for her bad luck Tessie might have made a heroic speech about the injustice of the practice and die with dignity. Perhaps that might have helped lead to change.